Method of manufacturing laminated mold and laminated mold

ABSTRACT

For manufacturing the laminated mold comprising the laminate ( 11 ) being formed of a plurality of thin sheets ( 11   a ) laminated on each other, laminate the thin sheets with the excess portions of respective thin sheets exceeding the profile of the tire crown portion on the side of contacting with the tire stepping face left, then remove the excess portions, form the sector mold by placing the laminate ( 11 ) with the excess portions removed in the holder, form the laminated mold having the annular read pattern by arranging a plurality of the sector mold in a peripheral direction of the tire so as to suppress formation of the stepped shape appearing on the tire profile comparing with the one as originally intended.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Present invention relates to a manufacturing method of a tire mold formolding a tire with vulcanization and specifically related to thelaminated mold provided with a laminate consisting of a plurality ofthin sheets laminated on each other in a widthwise direction and amanufacturing method thereof.

2. Description of the Prior Art

As shown by FIG. 8( a) and FIG. 8( b), so far has been used avulcanization metal mold (50) comprising a plurality of sector molds(53) annularly coupled each of which is formed of a holder (52) by whicha crown portion metal mold (51) having a cross sectional shape of thetire crown portion is held and the surface of a raw tire being alreadymolded is press fit to an inner wall of the heated vulcanization mold(50) by pressurizing inner side of the molded tire and such applicationof heat and pressure to raw rubber has been employed as a method ofvulcanization of tire. Usually, the above crown portion metal mold (51)can be manufactured by casting and yet, because such a casting mold notonly costs much labor but also material cost is high, recently formeeting purpose of attaining low cost and reduction in delivery date inplace of the above crown portion metal mold (51), which is a castingmold, a laminated mold as shown by FIG. 9( a) and FIG. 9( b) has becomein use wherein the laminated mold comprises an annular tread patternmolding portion being formed by arranging a plurality of sector molds(63) in a peripheral direction of the tire wherein the crown portionmetal mold (61) which consists of the laminate being formed of aplurality of thin sheets laminated, held by the holder (62) constitutesthe sector mold (63). In this description (61 s) denotes a laminationsurface of the thin sheet (61), (61 p) denotes an end face of the thinsheet on the side of the holder (62) and (61 q) denotes an end face ofthe thin sheet on the side of contacting with the face of the tirestepping on the road surface (hereinafter, the wording “the face of thetire stepping on the road surface” is shortened to read “the tirestepping face”).

In view of automating and speeding up the manufacturing, the thin sheet(61 a) is generally formed by means of a laser machining with 2DCAM.Thus formed thin sheets (61 a) are laminated to form the laminate to beused as the crown portion metal mold (61) and by placing the crownportion metal mold (61) in the holder (62), the sector mold (63) havingthe laminate as the crown portion metal mold can be formed. Concretelyspeaking, as shown by FIG. 10 the thin sheet materials (61 z) are cut atrespective both ends by casting a laser beam perpendicularly to thosethin sheet materials (61 z) to become rectangularly shaped cross sectionand those thin sheet (61 a) having thus formed rectangularly shapedcross section are laminated in a widthwise direction of the tire to formthe tread pattern molding portion.

However, as long as relying on the above method, as shown by FIG. 9( a)due to the fact that the cross section of the thin sheet (61 a) isrectangularly shaped, the crown portion metal mold (61), which is formedby coupling end faces (61 q) of respective thin sheets (61 a),inevitably becomes to have a profile stepped by the amount correspondingto the thickness of the thin sheets (61 a) having the rectangularlyshaped cross section. Accordingly, there have arisen problems such thatnot only appearance of the vulcanized tire is inferior but also itsperformance is inferior than that of the vulcanized tire manufacturedthrough the casting mold currently in use. Furthermore, possibility ofdegradation in durability is anticipated because many protrusions withacute angle appear on the tire stepping face.

Further, in the case where the thin sheets are laminated in a peripheraldirection of the tire, though close contact between those thin sheetscan be assured on the inner side of radial direction, but on the outerside thereof gaps are inevitably produced therebetween and not onlyopening and closing operation of the mold becomes unstable but alsodegradation in its durability will be caused.

The present invention is made to cope with those problems so far havearisen and thus object of the present invention to provide a method formanufacturing the laminated mold capable of suppressing formation ofstepped shape appearing on its profile comparing with the one asoriginally intended.

SUMMARY OF THE INVENTION

The invention of the second aspect provides the manufacturing method ofthe laminated mold comprising the laminate being formed of a pluralityof thin sheets laminated in a widthwise direction or in a peripheraldirection of the tire, and the manufacturing method is characterized incomprising the steps of laminating those thin sheets under the conditionthat the excess portions of them, which exceed the shape of the tirecrown portion, are left on the side contacting with the tire steppingface, and after proceeding the lamination step removal of the excessportions is carried out by means of a shot blast. By virtue of such aprocess, the profile of the laminated mold on the side of the tirestepping side can be formed quite the same with that of the tire asoriginally intended, and as a result the tire, which has both of theprofile and the performance equivalent to those obtained through thecasting mold currently in use, can become to be realizable easily. It isnoted that, though the profile of the tire crown portion as given aboveis generally meant by that which is taken in a widthwise direction butnevertheless the present invention also includes the profile taken in aperipheral direction of the tire crown portion such as change in depthof grooves in a peripheral direction of the tire.

The manufacturing method of the laminated mold according to theinvention of the third aspect is characterized in that the material tobe injected (hereinafter “the material to be injected” shortened to read“injection material”) according to the invention of the second aspect islimited to aluminum powder.

The manufacturing method of the laminated mold according to theinvention of the fourth aspect characterized in that removal of theexcess portions according to the second aspect or the third aspect iscarried out after masking boundary portions of respective thin sheets.

The invention of the fifth aspect provides the manufacturing method ofthe laminated mold comprising the laminate being formed of a pluralityof thin sheets laminated in a widthwise direction or in a peripheraldirection of the tire, wherein those thin sheets on the side of the tirestepping face are tapered in advance so as to bring those taperedportion thereof to have the taper angle approximately equal to the anglecorresponding to that of the profile of the crown portion and aftertapering them those tapered thin sheets are laminated. Through thisprocess of manufacturing method, by a simple machining the profile ofthe laminated mold on the side of the tire stepping face can beapproximated to the one as originally intended.

The manufacturing method of the laminated mold according to theinvention of the sixth aspect, the tapering work according to the fifthaspect is carried out by a laser machining.

The manufacturing method of the laminated mold according to theinvention of the seventh aspect the tapering work according to the fifthaspect is carried out by means of a shot blast.

The manufacturing method of the laminated mold according to theinvention of the eighth aspect is characterized in that when laminatinga plurality of thin sheets in a peripheral direction of the tireaccording either one of the first through seventh aspect, bumps areprovided on respective lamination surfaces of thin sheets in athicknesswise direction thereof, those thin sheets are caused tomutually abut therebetween in a lamination direction through those bumpsso as to secure those thin sheets with a fixed spacing, enabling tosecure them in a close contact therebetween, thereby stabilizing openingand closing operation of the mold and also improving the durability ofthe mold further.

The invention of the ninth aspect provides the laminated mold comprisingthe laminate being formed of a plurality of thin sheets laminated in awidthwise direction of the tire characterized in that bumps are providedon the lamination surfaces of respective thin sheets protruding in athicknesswise thereof so that those thin sheets are caused to mutuallyabut in a laminationwise direction, there by securing those thin sheetswith a fixed spacing.

The laminated mold according to the invention of the tenth aspectcharacterized in that the bumps provided on respective thin sheetsaccording to the ninth aspect are formed by a press work.

The laminated mold according to the eleventh aspect characterized inthat the thickness of the thin sheets according to the ninth or tenthaspect is limited to fall in the arrange of 0.1˜3 mm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a constitution of the sector mold used for the laminatedmold presented in the most preferable Embodiment 1 of the presentinvention.

FIG. 2( a) and FIG. 2( b) shows a working process for forming thelaminate presented in the most preferable Embodiment 1 of the presentinvention.

FIG. 3( a) and FIG. 3( b) show another example of constitution of thesector mold used for the laminated mold of the present invention.

FIG. 4( a) and FIG. 4( b) show a working process for forming the thinsheets used for the laminated mold as given in FIG. 3.

FIG. 5( a), FIG. 5( b) and FIG. 5( c) show a method of laminating thinsheets having bumps according to the present invention.

FIG. 6( a) and FIG. 6( b) show another example of working process forforming the laminate according to the present invention.

FIG. 7( a) and FIG. 7( b) show a working process for forming the thinsheets presented in the most preferable Embodiment 2.

FIG. 8( a) and FIG. 8( b) show a schematic diagram of a vulcanizationmetal mold of the prior art.

FIG. 9( a) and FIG. 9( b)show a schematic diagram of a laminated mold ofthe prior art.

FIG. 10 shows a working process for forming a thin sheet of the priorart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the present invention will be described hereinunder with reference to the accompanying drawings.

FIG. 1 shows a constitution of the sector mold (10) used for thelaminated mold exemplified in the most preferable Embodiment 1 and inthis drawing the reference numeral (11) denotes the laminate (crownportion metal mold) consisting of a plurality of thin sheets (11 a)laminated in a widthwise direction of the tire, (12) denotes the sectorholder (hereinafter named as “holder”) for holding the laminate (11)therein. In this Embodiment, when forming the laminate (11) as shown byFIG. 2( a) those thin sheets (11 a) are laminated under the conditionthat the excess portions, which is the portion exceeding the profile ofthe tire crown portion (tire profile) as denoted by the line L, are leftto the end face (11 q) of respective thin sheets (11 a) on the sidecontacting with the tire stepping face, and after those thin sheets havebeen laminated, as shown by FIG. 2( b) the excess portions are removedby means of a machining so as to reduce the profile of the mold on theside of the tire stepping face to the tire profile L as originallyintended. By virtue of this process, profile of the laminate (11) of thetire stepping face, which so far has been obliged to exhibit the shapestepped by the level difference corresponding to the thickness of therespective thin sheets (11 a), can be reduced to a smooth shape quitethe same with that of a casting mold currently in use.

Accordingly, as shown by FIG. 1, by arranging a plurality of sectormolds (10), which is formed by arranging the crown portion metal moldconsisting of the laminate (11) held in the holder (12), in a peripheraldirection of the tire, the laminated mold having the annular treadpattern mold can be formed. The vulcanized tire obtained through thusformed laminated mold is now released from exhibiting the appearance ofstepped shape resulting in that the tire having the same performancewith the one which is vulcanized through the casting mold currently inuse is available with low cost and in a shortened period.

In the most preferable Embodiment 1 as above, though description wasmade in the case where a plurality of thin sheets (11 a) are laminatedin a widthwise direction of the tire and nevertheless as shown by FIG.3( a) and FIG. 3( b) the present invention is also applicable tomanufacture the sector mold (10A) comprising the holder (12) for holdingthe laminate (13) being formed of a plurality of thin sheets (13 a)laminated in a peripheral direction of the tire. In this case, as shownby FIG. 4( a), the thin sheets (13 a) are laminated under the conditionthat the excess portions, appearing at an end face (13 q) of respectivethin sheets (13 a) on the side of the tire stepping face are left takingaccount of the profile taken in a peripheral direction of the tire asdenoted by K such as change in depth of grooves of the tire in itsperipheral direction, and as shown by FIG. 4( b) after proceeding thelamination the excess portions are removed by a machining work so thatthe profile of the mold on the side of the tire stepping face become thesame with that which is originally intended.

It is noted that, in the case where a plurality of the thin sheets (13a) are laminated in a peripheral direction of the tire, though on theinner side of a radial direction, i.e. on the side of the tire steppingface respective thin sheets (13 a) contact closely as shown by FIG. 5(a) and FIG. 5( b), but on the outer side as thereof shown by FIG. 5( c)gaps are obliged to be produced. To cope with this situation, it ispreferable to provide a plurality of bumps (14 a, 14 b, 14 c) protrudingin a thicknesswise direction of respective thin sheets (13 a) on theirrespective lamination surfaces (13 s) and as shown by FIG. 5( c) arrangethose the thin sheets (13 a) to cause to mutually abut in alaminationwise direction between those thin sheets, so as to secure afixed spacing therebetween. As a result, close contact between thosethin sheets (13 a) can be made securely and opening and closingoperation of the mold can be stabilized and also durability of the moldcan be improved.

As to the foregoing structure, it is quite natural that the amount ofthe protrusion (14) of the bumps are set higher as they go outwardly ofradial direction. Concretely speaking, amount of the protrusion H isgiven by the formula 1, wherein A denotes radius of the thin sheet (13a) up to the inner end in radial direction, B denotes radius of the thinsheets (13 a) up to the outer end in radial direction, C denotes thedimension covering the distance from outer end of the thin sheet (13 a)in a radial direction to the bump (14) and t denotes the thickness ofthe thin sheet. Thus, Formula (1) is given as,Protrusion height H={π(B−2C)−πA}/(πA/t)   {circle around (1)}

It is noted that provision of forming bumps (14) on the thin sheets (13a) can be easily made by means of applying a press molding to the metalsheet. In view of workability, thickness of the above metal sheet (theshin sheet (13 a)) is preferably chosen to fall in the range of 0.1˜3 mmwhen the thin sheet is formed by means of a press molding.

In the above example, though description was made in the case ofremoving the excess portions by means of a machine work, and yet othermeans such as a laser machining or a shot blast can be applicable toperform such a removal of the excess portions and this is done as shownby FIG. 6( a) such that compressed air, which is mixed with an injectionmaterial in a state of minute particles (15 p) such as abrasive sand, isforcibly sent and is blasted on to the surface of the laminate (11)through a nozzle (15), thereby polishing the inside surface of thelaminate. The materials to be sprayed are chosen depending on thematerial to be polished and attached material among various materialssuch as fragments of metals such as iron, copper, zinc, and aluminum andglass beads and ceramic powder. Among them, ceramic powder having minutediameter of particles and high hardness is preferable and still use ofaluminum powder is specifically preferred.

As shown by FIG. 6( b) prior to perform the shot blast, it is preferableto coat the stepped valley portion (11 k) which is a boundary portionbetween those thin sheets (11 a), with a removable masking material (16)by peeling off such as vinyl chloride by spraying the above material tothat portion (11 k) and after that it is preferable to polish them by ashot blast. In this manner after performing the shot blast profile ofthe laminate on the side of the tire stepping face can be reducedcertainly to a smoothly finished surface being the same with that whichis obtained by means of casting mold currently in use. Furthermore, byperforming the above mentioned masking the thin sheets (11 a) areprotected from entering of sprayed powder and fragments into minute gapsbetween those thin sheets (11 a) and in turn those minute gapstherebetween can be alive, thereby securing the passages for releasingair through those gaps during the mold being proceeded.

The Most Preferable Embodiment 2

Though in the Embodiment 1, the profile of the mold on the side of thetire stepping face was reduced to the shape quite the same with thatwhich is denoted by L obtained by removing the excess portions by amechanical work after laminating those thin sheets (11 a) with thoseexcess portions left thereto, and still other than the foregoing asshown by FIG. 7( a) a laser work can be applicable such that thelaminate (crown portion metal mold) (11A) consisting of thin sheets (11a) laminated can also be formed in such a manner that firstly the thinsheets (11 a) to be laminated on the side of contacting with the tirestepping face are tapered by means of a laser machining device (18)having a laser generator (17) so as to make the angle essentially thesame with the angle corresponding to the profile of the crown portion,and after that those thin sheets (11 a) which have been thus tapered,are laminated to form the laminate (11A). In this manner, as shown byFIG. 7( b) by a simple working, profile of the mold on the side of thetire stepping face can be approximated to the tire profile L asoriginally intended. In this example, profile of the laminate (11A) onthe side of the tire stepping face becomes to the shape as shown by thebroken line and this manifests that, if the condition that thickness andnumber of thin sheets (11 a) to be laminated are properly set, thevulcanized tire can be reduced to a sufficiently smooth form. It isnoted that the foregoing tapering work is not limited to the lasermachining but other means such as mechanical machining and shot blastcan be applicable.

INDUSTRIAL FEASIBILITY

As hitherto mentioned, according to the present invention whenmanufacturing the laminated mold either one of procedures can beemployed: first, thin sheets are laminated under the condition thatexcess portions of respective thin sheets on the side of the tirestepping face, namely the portions exceeding the profile of the tirecrown portion, are left and after the lamination proceeded those excessportions are removed, or alternatively, the thin sheets on the side ofthe tire stepping face are tapered in advance so that the taperedportions exhibit substantially the same angle that which corresponds tothe profile of the tire crown portion and after this tapering work thosethin sheets are laminated and thus the profile of the laminated mold onthe side of the tire stepping face can be made the same with orapproximately the same with the profile as originally intended. In thismanner, the tire having the same profile with that which so far has beenmanufacture by means of the casting mold currently in use can berealized with low cost and in a shortened period.

1. A manufacturing method of a laminated mold comprising a laminatebeing formed by laminating a plurality of thin sheets in a widthwisedirection or in a peripheral direction of a tire comprising the stepsof, laminating the thin sheets having rectangular cross section so as tobring the thin sheets on the side of contacting with a tire steppingface to be placed along a profile of a tire crown portion, and afterlaminating the thin sheets, excess portions of respective thin sheetsexceeding the profile of the tire crown portion are removed by means ofa shot blast.
 2. The manufacturing method of the laminated moldaccording to claim 1, characterized in that aluminum powder is used asthe material to be injected.
 3. The manufacturing method of thelaminated mold according to claim 2 characterized in that, after maskingboundary portions of respective thin sheets, removal of the excessportions is performed by means of blasting.
 4. The manufacturing methodof the laminated mold according to claim 2, when laminating a pluralityof the thin sheets in a peripheral direction of the tire comprising thesteps of, providing bumps on lamination surfaces of respective thinsheet in a thicknesswise thereof so that the thin sheets are caused tomutually abut in a laminationwise direction through the bumps so as tofix spacing between the thin sheets.
 5. The manufacturing method of thelaminated mold according to claim 1 characterized in that, after maskingboundary portions of respective thin sheets, removal of the excessportions is performed by means of blasting.
 6. The manufacturing methodof the laminated mold according to claim 5, when laminating a pluralityof the thin sheets in a peripheral direction of the tire comprising thesteps of, providing bumps on lamination surfaces of respective thinsheet in a thicknesswise thereof so that the thin sheets are caused tomutually abut in a laminationwise direction through the bumps so as tofix spacing between the thin sheets.
 7. The manufacturing method of thelaminated mold according to claim 1, when laminating a plurality of thethin sheets in a peripheral direction of the tire comprising the stepsof, providing bumps on lamination surfaces of respective thin sheet in athicknesswise thereof so that the thin sheets are caused to mutuallyabut in a laminationwise direction through the bumps so as to fixspacing between the thin sheets.
 8. The manufacturing method of thelaminated mold according to claim 1, when laminating a plurality of thethin sheets in a peripheral direction of the tire comprising the stepsof, providing bumps on lamination surfaces of respective thin sheet in athicknesswise thereof so that the thin sheets are caused to mutuallyabut in a laminationwise direction through the bumps so as to fixspacing between the thin sheets.